20 ATTACHMENT 3 - Laserfiche WebLink

Updated Arborist Report Sarvana Chilla, 3987 Sta HortScience I Bartlett Consulting Page 4 The City of Pleasanton Municipal Code (Chapter 17.6) defines a Heritage tree as having either a trunk diameter of 18" or greater or a height of 35' or greater. Two valley oak trees meet both criteria. One tree was located on the property line (#18) the one was an off-site tree (#17). Suitability for Preservation Before evaluating the impacts that will occur during development, it is important to consider the quality of the tree resource itself, and the potential for individual trees to function well over an extended length of time. Trees that are preserved on development sites must be carefully selected to make sure that they may survive development impacts, adapt to a new environment and perform well in the landscape. Our goal is to identify trees that have the potential for long-term health, structural stability and longevity. For trees growing in open fields, away from areas where people and property are present, structural defects and/or poor health presents a low risk of damage or injury if they fail. However, we must be concerned about safety in use areas. Therefore, where development encroaches into existing plantings, we must consider their structural stability as well as their potential to grow and thrive in a new environment. Where development will not occur, the normal life cycles of decline, structural failure and death should be allowed to continue. Evaluation of suitability for preservation considers several factors: • Tree health Healthy, vigorous trees are better able to tolerate impacts such as root injury, demolition of existing structures, changes in soil grade and moisture, and soil compaction than are non -vigorous trees. For example plum (#4) had multiple trunks growing through metal wire located at the base of the tree. The lack of proper maintenance had weakened the tree and it may not handle construction impacts as well as a healthier tree. • Structural integrity Trees with significant amounts of wood decay and other structural defects that cannot be corrected are likely to fail. Such trees should not be preserved in areas where damage to people or property is likely. • Species response There is a wide variation in the response of individual species to construction impacts and changes in the environment. Italian alder with adequate irrigation has good tolerance to construction impacts and valley oak has moderate tolerance to construction impacts. • Tree age and longevity Old trees, while having significant emotional and aesthetic appeal, have limited physiological capacity to adjust to an altered environment. Young trees are better able to generate new tissue and respond to change. • Species invasiveness Species that spread across a site and displace desired vegetation are not always appropriate for retention. This is particularly true when indigenous species are displaced. The California Invasive Plant Inventory Database (http://www.cal-ipc.orq/paf/) lists species identified as being invasive. Pleasanton is part of the Central West Floristic Province. There were no species on this site found on the invasive plant inventory list.